In heart surgery that involves cardiac arrest in a patient, a heart-lung machine is used for taking over the functions of respiration and circulation during the cardiac arrest. Further, during the surgery, it is necessary to lower the patient's temperature and maintain the same so that the patient's oxygen consumption should decrease. For this purpose, the heart-lung machine is equipped with a heat exchanger to control the temperature of blood taken out of the patient.
As such a medical-use heat exchanger, a bellows-type heat exchanger (see Non-Patent Document 1, for instance), a multi-tubular heat exchanger (see Patent Document 1, for instance), etc., have been known conventionally. Among these, the multi-tubular heat exchanger has a larger area used for heat exchange as compared with the bellows-type heat exchanger with the same device capacity, and hence, it has the advantage of a higher heat exchange ratio as compared with the bellows-type heat exchanger. Accordingly, the use of the multi-tubular heat exchanger is considered to contribute to the downsizing of the heart-lung machine.
Here, the conventional multi-tubular heat exchanger is described specifically with reference to FIGS. 10A, 10B, and 11. FIGS. 10A and 10B show a conventional multi-tubular heat exchanger. FIG. 10A is a top view of the same, while FIG. 10B is a front view of the same. FIG. 11 is a perspective view illustrating tubes and sealing members composing the conventional multi-tubular heat exchanger shown in FIGS. 10A and 10B. The heat exchanger shown in FIGS. 10A and 10B is a heat exchanger for medical use.
As shown in FIGS. 10A, 10B, and 11, the conventional multi-tubular heat exchanger includes a plurality of tubes 31 through which blood taken out of a patient flows, a housing 32 for housing the tubes 31, and sealing members 33a and 33b. The sealing members 33a and 33b are disposed at ends of the tubes 31 on opposite sides, respectively, so as to seal cold/hot water (heat medium) flowing over surfaces of the tubes 31. Besides, the tubes 31 are fixed in the housing 32 by the sealing members 33a and 33b. The tubes 31 are arrayed regularly at uniform pitches as shown in FIGS. 10A, 10B, and 11 to improve the heat exchange ratio. It should be noted that arrows in FIG. 10A indicate a direction of blood flow, and arrows in FIG. 10B indicate a direction of flow of cold/hot water.
A space between the sealing members 33a and 33b in the housing 32 constitutes a flow path through which cold/hot water flows. Besides, the sealing members 33a and 33b are formed in a manner such that they are in close contact with internal faces of the housing 32 and external faces of the tubes 31, whereby the sealing of cold/hot water flowing the flow path is achieved. The housing 32 is provided with an inlet 34 and an outlet 35 for cold/hot water whose positions are matched to positions of mouths of the flow path for cold/hot water.
Thus, in the heat exchanger shown in FIGS. 10A, 10B, and 11, when blood flows in through the tubes 31 while cold/hot water flows in through the inlet 34, heat exchange occurs between blood and cold/hot water via tube walls of the tubes 31, whereby the temperature of blood is adjusted. Besides, mouths of the tubes 31 on the blood outlet side are connected to an artificial lung (not shown), and blood thus subjected to temperature adjustment is fed to the artificial lung. In the artificial lung, addition of oxygen and discharge of carbon dioxide are carried out on the blood.
The heat exchanger shown in FIGS. 10A, 10B, and 11 is formed with the following procedure. First, a plate (not shown) provided with a plurality of through holes is prepared, and tubes 31 are inserted into the through holes (not shown) of the plate, respectively. Then, the tubes 31 in this state are housed in a housing 32, and the first potting is performed. Further, in a state in which the plate is removed, the second potting is performed, whereby the sealing members 33a and 33b are completed. Thus, the multi-tubular heat exchanger as shown in FIGS. 10A, 10B, and 11 is obtained.
Patent document 1: JP 11 (1999)-47269 A (FIGS. 4 and 10)
Non-patent document 1: “TRILIUM AFFINITY NT Oxygenator” Medtronic, 2000, U.S.